OK, thanks, so those holes are just for inserting a pry bar to turn the whole ring. Also I discovered a hex nut in the end of the knob without the markings which was loose. Gently hand tightening removed the slack which had allowed them to be pulled out and left the friction too loose. Now it's working nicely.

So I did a wood mock-up & mounted it in the simplest way to test and it does not work well at all. Very bouncy! You can see it looks like a swimming pool diving board. Usability is fantastic though. In theory I could add short 'wings' to make a reinforced I-beam and steel should be better than this hard wood but this is so bad, I don't think it's the right way to go. The final design was intended to snug the block under the arm, not on the end like this but still.

The only solution I can see is have a quick release plate drilled and screwed directly onto the focus block which is going to be rather thick so also use a shorter bellows like PB-5.

Or set up the focus block on the stage like the tilt goniometer shown, which also isn't simple. Hmph!

For magnification, I'm thinking of moving from 10x 0.30 NA to 20x 0.65, maybe 40x, maybe 10x 0.45 at 20x. I can currently just manage 2 micron steps, (average) comfortably (a little less than half a 5-micron tick mark) using a micrometer screw on the front of the bellows and have used that at 20x with a 10x objective on this rig when the wind isn't blowing the building around, rattling the windows. It is somewhat questionable whether the bellows will be capable of 40x, for stability but there's always the option of mounting the camera direct with extension tubes. It's also questionable whether I can comfortably get 1 micron steps with this focus block (half tick marks). I should have played with that more before disassembling... I guess I should reassemble & check that.

The 30mm of travel will also be useful down to probably around 5x and even for fine focus using it as a copy stand for letter sized subjects.

Seems it will still be possible to do this, it will just take some pretty fancy metalwork:

1. Mount a thin plate over the focus block with a 1/4-20 tripod screw (welded on?) (and some way to tighten it in the right alignment???).

2. Cutting back the aluminum focus block to fit, with some type of router cutting away areas that can't be reached without disassembling it. Perhaps it's safe to loosen the hex nut in the unmarked end of the FF knob and pull the knobs off but I doubt it.

3. Mounting to the cast iron focus arm tube: maybe cut the bottom off and grind the focus block down to slide in, then screws from the side like I've done with wood. The current wood 'plug' is not seen clearly in the photos but it is rock solid. I've returned the bellows to that mount for now.

I managed to make a flush metal tripod mounting plate with a piece of 1/4" steel that I had handy and a countersunk 1/4-20 screw with over-sized philips head, so that part worked great. The wood 'plug' that I described as rock solid is not solid in this configuration - essentially the same as shown above without the 'diving board'. But I put some blocking under the focus block to secure it against the stage and that's pretty reasonable. It still shows bumps in the floor, etc but dampens out in a fraction of a second so my typical 2 sec exposures are good. And I *can* make 1 micron steps with it loaded. Now to figure out how to cut it back & mount it properly to the focus arm of the scope.

This is a test stack of 7 frames, lower right corner crop, 1 micron steps at 18x with the 10x 0.3 NA on D700, 2 seconds. Smoked glass from a match with dust. This is the sort of detail where shooting raw might be wise, I used jpegs:

Here's some crude illustrations. Sorry it's messy but I took care to show the relevant angles and this serves as my notes as I study, not final lecture slides. As shown, it is impractical to grind down the sides but I think there's still hope. The basic final form is correct, probably the solution is to cut off all of the cast iron focus arm tube except for the top surface, along the dashed line shown and use that top plate to tap screws into the aluminum focus block below with gravity holding the rest in place. As you can see, the final setup would be a *lot* more stable than the temporary mock-ups shown. The second portrait oriented pic is a rough photoshop assembly in the position I have in mind.

Challenges for the next idea include un-screwing the focus knobs to allow a saw to cut the line drawn as drawn and cutting off the cast iron focus arm with difficult access.

I did it. And it is rock solid again, although I don't have the tools to make it all come together neatly. I guess I'll have to find a machine shop to finalize things. This shows the focus block cut back with about 1/3 of the post hole gone, so it is just barely possible to center over the rotating stage. The big 1/2" bolt runs through the remaining 2/3 of the post hole. I cut off all but the top 'shelf' of the focus arm which is drilled for the big bolt. It would have been possible to cut closer by putting the hack saw blade inside the post hole & cutting outward in each direction but awkward for a number of reasons. I've got an 1/8" slab of metal wedged in the gap to the right to tighten things up for this trial run. Ideally it will have a quick release hand tightened knob on top and a new tripod screw hole so it can be transferred to a tripod for horizontal use. Before cutting, there was a tripod screw hole and it worked nicely in that arrangement.

Final working version of the Zeiss Jena Large Toolmaker's Microscope with Olympus BHMJ focus block and Nikon PB-4 bellows

This really is final. I promise. I borrowed a friend's shop for the afternoon. Band saw, table saw with grinder blade and thread tap for two 1/4-20 bolts on top and one hidden inside, below. The block is cut way back so it's centered on the stage properly and the rusty old slab of steel is ground down to clean metal. I left the 'diving board' for gauging stacks: this shows a bit of blue painter's tape on it but a magnetic strip works better to mark start/end points for a stack. It is not easily removable nor can it mount to a tripod as I had hoped. It would be great if I got another vertical arm from one of these old rigs for working horizontally

Rather than butcher a microscope it is preferable to install a new platform above the microscope frame. This has 3 advantages over a butchered stand:
1] The scope remains intact and fully functional (have to remove the platform and re-attach the head).
2] The new platform can be much larger than the microscope's stage, allowing plenty of room to hold the specimen, light diffuser, and even flashes (see photo).
3] There is no vertical component to get in the way of the new platform. In the original butchered scope the remaining upright restricted full access to the stage.

The only requirement is for a microscope that allows for the head (the piece that holds the eyepieces) to be removed.

The Blow Fly image
http://www.photomacrography.net/forum/viewtopic.php?t=14996&sid=de82137440bfbcfb20efee61dc9b189c
was taken with this set up.
NU11144_________________NU.
student of entomology
Quote – Holmes on ‘Entomology’
” I suppose you are an entomologist ? “
” Not quite so ambitious as that, sir. I should like to put my eyes on the individual entitled to that name.
No man can be truly called an entomologist,
sir; the subject is too vast for any single human intelligence to grasp.”
Oliver Wendell Holmes, Sr
The Poet at the Breakfast Table.

Not sure if the built-in microscope lamp and condenser would be of any use when the platform is such a long distance from it.
The scope's neck has a hole, of course, for the objective holder. One could simply lay a flash on the wooden stage, or place a white card there and direct a light onto it.

Specimen too high?? I stand up, the stage is only 1.1 meters (43 inches) above the floor._________________NU.
student of entomology
Quote – Holmes on ‘Entomology’
” I suppose you are an entomologist ? “
” Not quite so ambitious as that, sir. I should like to put my eyes on the individual entitled to that name.
No man can be truly called an entomologist,
sir; the subject is too vast for any single human intelligence to grasp.”
Oliver Wendell Holmes, Sr
The Poet at the Breakfast Table.

Some of my first stacking was done with an old Vickers scope which came for £20 (Approx US$30) with the focus and stage movements working. I did what NU is suggesting in effect, by laying an old drawer on its side, on the stage. It was a narrow metal drawer, of the type usually used for nuts and bolts, but anything small would have done.

I also used a length of pipe, resting one end on the stage with the other poking up through the hole where the head was missing. (without the drawer!)
(Then, never likely to get a head, I used a holesaw to make a hole through the arm large enough for 39mm tubes. Stepping the 39mm up to 52mm gave a shoulder which held the tubes, with the camera on top. But that's breaking the rules!)

I did what NU is suggesting in effect, by laying an old drawer on its side, on the stage.

And I thought my idea was original. Perhaps delayed telepathy.

Note: it's important that the 'new stage' be attached to the slider of the microscope stage for accurate moving._________________NU.
student of entomology
Quote – Holmes on ‘Entomology’
” I suppose you are an entomologist ? “
” Not quite so ambitious as that, sir. I should like to put my eyes on the individual entitled to that name.
No man can be truly called an entomologist,
sir; the subject is too vast for any single human intelligence to grasp.”
Oliver Wendell Holmes, Sr
The Poet at the Breakfast Table.

Yours is a more elegant implementation!
My stage had a plate on it which moved with the x-y controls. I put a couple of heavy vee-blocks in the drawer to hold it down. My problem was with the column being too springy though.

It seems there's not much new in the world. If it wasn't the Victorians it was the Greeks...